Videos posted online Friday apparently shot inside the base say Jabhat al-Nusra participated in the overnight battle for the base. The videos show fighters inspecting lines of large missiles.

Two Aleppo-based activists and Rami Abdul-Rahman, head of the Syrian Observatory for Human Rights, also say Jabhat al-Nusra fought in the battle.

The base’s capture is sure to fuel fears that Islamic extremists are playing a greater role after nearly 19 months of unrest in Syria. Western powers cite their presence as a reason not to arm the rebels.

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Syrian opposition activists estimate more than 32,000 people have been killed since March 2011 when the uprising against Assad’s regime began.